# First, let's define some basic sets of words (with common abbreviations)
$days = 'Sun(day|\.)?|      # All of these may be abreviations, 
         Mon(day|\.)?|      #   with or without a period
         Tues?(day|\.)?|    # Accept Tue or Tues
         Wed(nesday|\.)?|
         Thurs?(day|\.)?|   # Accept Thur or Thurs
         Fri(day|\.)?|
         Sat(urday|\.)?';
$months = 'Jan(uary|\.)?|
         Feb(ruary|\.)?|
         Mar(ch|\.?)|
         Apr(il|\.)?|
         May|
         Jun(e|\.)?|
         Jul\.|
         Aug(ust|\.)?|
         Sept?(ember|\.)?| # Accept Sep or Sept
         Oct(ober|\.)?|
         Nov(ember|\.)?|
         Dec(ember|\.)?';
$time_units = 'sec(onds?|\.)?|
         min(utes?|\.)|
         hours?|hrs?.?|    # Accept hr or hrs
         days?|
         weeks?|
         months?|
         years?';
         
# An admittedly incomplete list of "special" holidays
$holiday1 = 'Christmas|Easter|Thanksgiving|Halloween|
             Ramadan|Mardi Gras|Passover|Kwanza|Chanukah';

# $holiday2 includes holidays like "Mother's Day" and "St. Patrick's Day".
#   This figures out how many words are part of the holiday name based on
#   capitalization.  Thus, it won't work quite right on a phrase like
#   "It's Groundhog's Day" because it will include "It's" within the TIME tag.  

$holiday2 = '([A-Z][\w\'\.]*\s*)*  # Mutliple copies of capitalized "words" 
         (Day|Eve)';               # A trailing (capitalized) "Day" or "Eve" 
                                   #   tells us it's probably a holiday

# All of the basic sets above
$basics = "$days|$months|$time_units|$holiday1|$holiday2";



# Various numerical forms which will be used below
$one_to_9 = '[Oo]ne|[Tt]wo|[Tt]hree|[Ff]our|
             [Ff]ive|[Ss]ix|[Ss]even|[Ee]ight|[Nn]ine';
$ten_to_12 = '[Tt]en|[Ee]leven|[Tt]welve';
$thirteen_to_19 = '[Tt]hirteen|[Ff]ourteen|[Ff]ifteen|
              [Ss]ixteen|[Ss]eventeen|[Ee]ighteen|[Nn]ineteen';
$twenty_to_31 = "[Tt]wenty(-($one_to_9))?|[Tt]hirty(-one)?";

# For months where we only expect numbers 1 to 31
#    Inlcudes both numeric and alphabetic number forms
$all_num = "$twenty_to_31|$one_to_9|$ten_to_12|
            $thirteen_to_19|[12][0-9]|3[01]|[1-9]";

# Sometimes we need more than just 31 numbers
$tens = '[Tt]wenty|[Tt]hirty|[Ff]ourty|[Ff]ifty|
         [Ss]ixty|[Ss]eventy|[Ee]ighty|[Nn]inty';
$full_num = "(($one_to_9)\\s*                # (a number from one and nine
             [Hh]undred\\s*                  #  hundred
             (and\\s*)?)?                    #  (and) -- optional) -- optional
             ($one_to_9|                     # any number from one to ninety-nine
               $ten_to_12|
               $thirteen_to_19|
               ($tens(-($one_to_9))?))";

# "First", "Second", "Third" forms needed for "first of October" 
$first_to_ninth = '[Ff]irst|[Ss]econd|[Tt]hird|[Ff]ourth|
                  [Ff]ifth|[Ss]ixth|[Ss]eventh|[Ee]ighth|[Nn]inth';
$tenth_to_19th = '[Tt]enth|[Ee]leventh|[Tt]welvth|[Tt]hirteenth|
                  [Ff]ourteenth|[Ff]ifteenth|[Ss]ixteenth|
                  [Ss]eventeenth|[Ee]ighteenth|[Nn]inteenth';
$twentieth_to_31st = "[Tt]went((y-($first_to_ninth))|ieth)|[Tt]hirt((y-first)|ieth)";

# Numeric 1st, 2nd, 3rd forms
$numeric_th = '1st|2nd|3rd|20th|21st|22nd|23rd|30th|31st|[4-9]th|1[0-9]th|2[4-9th]';

# All of the above 1st/first forms
$all_th = "$twentieth_to_31st|$first_to_ninth|$tenth_to_19th|$numeric_th";



# Standard numeric forms for the year, from 1000-2999. 
#   Unless we're dealing with historical texts, any number outside of these ranges is likely
#   to not be a number.
$years = '[12][0-9]{3}';

# Ditto for decades, 1000's through 2990's (includes both "1990s" and "1990's")
$decades = '[12][0-p]0';

# I've NOT included alphabetic year forms (i.e., nineteen hundred ninety six)

# Some common date forms
$date1 = "(($days),?\\s*)?($months)\\s*        # March 5th, 1922 (year optional)
          ($all_th|$all_num)(,\\s*$years)?";
$date2 = "(($days),?\\s* )?($all_th)\\s*       # 5th of March, 1922 (year optional)
          of\\s*($months)(,\\s*$years)?";

# Numeric date forms for 1900s and 2000s (such as 11/29/01 or 29-11-2001)
$date3 = "([12][0-9]|3[01]|[1-9])-             # Day-month-year 
          ([1-9]|1[0-2])
          -(19|20)?[0-9]{2}";
$date4 = "([1-9]|1[0-2])\/                     # Month/day/year 
          ([12][0-9]|3[01]|[1-9])
          \/(19|20)?[0-9]{2}";
$date5 = "([1-9]|1[0-2])-                      # Month-day-year 
          ([12][0-9]|3[01]|[1-9])
          -(19|20)?[0-9]{2}";
$date6 = "([12][0-9]|3[01]|[1-9])\/            # Day/month/year 
          ([1-9]|1[0-2])
          \/(19|20)?[0-9]{2}";

# Centuries, from the 1st to the 31st
$century = "($all_th)\\s*[Cc]entury";

# All of the various date and year type forms given above
$all_dates = "$date1|$date2|$date3|$date4|$date5|$date6|$century|$decades|$years";




# Time-of-day forms.  I have not included international/military 24 hour clock times.
$vague_times = '[Mm]orning|[Nn]oon|[Aa]fternoon|[Ee]vening|([Tt]on|[Nn]|[Mm]idn)ight';
$o_clock = "($one_to_9|$ten_to_12|[1-9]|1[0-2])\\s*   # six o'clock
            (([Oo]\'\\s*clock)|                       # or 2am, 8 pm
            ([Aa]|[Pp])[Mm])";                        
$half_past = "[Hh]alf\\s*past\\s*                     # half past eight
            ($one_to_9|$ten_to_12|[1-9]|1[0-2])";
$quarter_form = "([Aa]\\s*)?[Qq]uarter\\s*            # (a) quarter to/after/past three
            (to|after|past)\\s*
            ($one_to_9|$ten_to_12|[1-9]|1[0-2])";
$colon_form = "([1-9]|1[0-2]):                        # standard 6:45am form
            [0-5][0-9](\\s*)?(([Aa]|[Pp])[Mm])?";

# All of the above time forms
$all_times = "$vague_times|$o_clock|$half_past|$quarter_form|$colon_form";



# Deictic expressions
$basic_deictic = '[Tt]oday|[Yy]esterday|[Tt]omorrow';
$special_deictic = '[Tt]he\s*day\s*                   # recognizes "the day before yesterday"
            (before\s*yesterday|after\s*tomorrow)';   #   and "the day after tomorrow"
$n_from_deictic = "($full_num|a|[0-9]*)\\s*           # six days from Sunday
            ($time_units)\\s*from\\s*                 #   or six minutes from now, etc.
            ($days|$basic_deictic|now)";
$ago_deictic = "($full_num|[0-9]*)\\s*                # Twelve days ago/hence/earlier etc.
            ($time_units)\\s*
            (ago|hence|before|after|later|earlier)";
$in_deictic = "([Ww]ithin|[Ii]n|                      # In/within/after/before eight minutes
             [Aa]fter|[Bb]efore)\\s*           
            ($full_num|[0-9]*)\\s*($time_units)";     
$next_deictic = "([Nn]ext)\\s*                
            ($days|week|month|year)";

# All of the previously defined deictic forms
$all_deictic = "$basic_deictic|$special_deictic|
                $n_from_deictic|$ago_deictic|$next_deictic|$in_deictic";